Don't require Title for getTimestampFromId

Don't require Title for getTimestampFromId

3e36ba655e3a added an option for passing a page ID to this method of
Revision, and e03787afd91c switched it to a Title and made it mandatory.
This behavior propagated to the method in RevisionStore.  As far as I
can tell, the parameter does not help anything, but it can add a
database query to get the page ID if it's not cached, and impedes
conversion to LinkTarget. I can't figure out any reason to not
completely drop it. I've noted it as deprecated but still supported it
for now for compatibility -- I found one extension that does pass it.
(It's ignored, though, which theoretically would be a behavior change if
someone was passing a Title that didn't match the revision ID.)

While I was at it, I added the method to RevisionLookup, although it's
only used in later patches. Properly I should move that piece to a later
patch, but it didn't seem worth the effort.

I didn't change the Revision method, because the whole Revision class is
deprecated anyway.

Change-Id: I26ef5f2bf828f0f450633b7237d26d888e2c8773